This invention relates to a reformer for a fuel system and a method for reforming fuel for a fuel cell system.
It is well known that fuel cells operate to react a fuel with air to generate electrical energy. The fuel is generally hydrogen that is derived from either methanol or a mixture of methanol and water. The fuel is reformed in a reformer in the presence of a catalyst and heat so as to provide the hydrogen. Obviously, the efficiency of the fuel cell can be improved by providing a longer reaction time within the catalyst. However, there is a practical limit to the size of the reformer that can be employed for obvious reasons. It has, therefore, been proposed to provide a reformer that has a relatively long catalyst path through which the fuel can travel so as to insure that all fuel is reformed.
However, there are additional difficulties in conjunction with the provision of such long catalyst paths in the reformer. This is because there are certain chemical reactions taking place in the reformer as set out below: EQU CH.sub.3 OH.fwdarw.CO+2H.sub.2 ( 1) EQU CO+H.sub.2 O.fwdarw.CO.sub.2 +H.sub.2 ( 2).
The first chemical reaction (equation 1) is an endothermic reaction, while the second (equation 2) is an exothermic reaction. However, the second equation tends to operate in the reverse direction in atmospheres of high temperature. When this occurs, then the CO content will increase and the fuel value will decrease. In addition, there may be attack of the platinum catalyst of the fuel cell. In the reformer systems previously proposed having long flow paths, the fuel reaching the end of the catalyst path may be heated to such a high elevation that the reverse reaction will occur with the aforenoted detrimental effects.
It is, therefore, a principal object of this invention to provide an improved reformer and method of reforming fuel wherein full reformation of the fuel can be assured without the generation of adverse components or constituents that could attack the catalyst of the fuel cell.
It is a further object of this invention to provide an improved compact reformer that will provide proper fuel reformation without generating components that could be dangerous to the performance of the fuel cell.